Greedy contractors working for the city cheated employees out of $4.2 million in wages – but now they have to pay it all back, authorities said.

The 147 workers who spent months on demolition and construction jobs for Corinthian Construction and D&S Plumbing/Zaffuto Construction will receive up to $50,000 each in back wages, said Attorney General Eliot Spitzer, who investigated the companies after workers discovered the rip-off.

“I’m so happy I want to do back flips,” said Arthur Jenkins, 30, a single father of five who made only $20 an hour helping renovate Ocean Bay Houses in Far Rockaway. “Me and my kids are going to have a field day – we’re going to Disney World!”

Jenkins was one of many laborers who received $15 to $20 an hour, authorities said, even though the state Labor Department required the contractors to pay them $30 an hour.

After a worker tipped the state to the low-balling tactics, Jenkins said, construction bosses threatened to fire anyone who talked to investigators.

None of the contractors will go to jail, but six – including several companies subcontracting with D&S/Zaffuto – pleaded guilty to felony charges.

D&S/Zaffuto itself did not plead guilty to a crime, and Andrew Lankler, a company attorney, insists subcontractors left the company “holding the bag.”

Nevertheless, the firm will pay back $1.8 million stolen from workers since 2001, and principals Angelo and Joseph Zaffuto were banned from accepting city or state contracts for five years, as was Corinthian.